1. Field of the Invention
This invention relates generally to dry barrel treating machine grinding, polishing or cleaning workpieces, and more particularly to a barrel container used with a dry barrel polishing machine.
2. Description of the Related Art
One type of barrel polishing machines uses a rotational barrel container. The barrel container includes a container body having an opening and a lid closing the opening of the container body. The container body comprises a casing generally made of steel and a lining made of an elastic material and attached to an inner wall of the casing. The lining relieves collision of polishing chips and workpieces against an inner wall of the barrel container during polishing, thereby preventing the steel wall of the container from wear. The lid also includes a steel base and a lining attached to the inside of the base. One or more barrel containers are mounted on a barrel polishing machine.
The aforesaid steel casing is made by bending a steel plate 39 as shown in FIGS. 10 to 12. For example, a container body 47 as shown in FIG. 12 has a hexagonal section and includes an opening 40 formed in one of the six sides thereof. In the manufacture of the container body 47, a steel plate 39 is bent so as to have a hexagonal section. Thereafter, two hexagonal steel plates 42 are welded to both open ends of the container body, respectively, so that a hollow casing 41 is formed. Previously divided cores 44a and 44b are then inserted through the opening 40 into the casing 41. The divided cores 44a and 44b are connected together in the casing 41 to be assembled into an integral core 44. A bridge member 31 is mounted between flanges 45 formed along peripheral edges of the opening 40. The core 44 is then hung on the bridge member 31. A material for a lining 46, for example, molten polyurethane resin, is poured into a space between an inner wall of the casing 41 and the core 44. The molten resin is cooled to be solidified such that a barrel polishing container 47 with the polyurethane lining 46 is formed.
There are two types of barrel polishing machines, namely, dry barrel polishing machines using no water and wet barrel polishing machines using water. In view of environmental protection and economy in treating costs, the dry barrel polishing machines have recently been predominant. Japanese Patent No. 2643103 discloses a barrel container used in the dry polishing. The disclosed barrel container includes an external air intake portion or vent formed in the casing or the lid for introducing external air into the casing. The container further includes a dust exhaust portion formed in the casing or the lid for exhausting dust resulting from polishing. The barrel container is attached to a polishing machine and rotated so that polishing chips and workpieces are moved at high speeds in the barrel container. As a result, the workpieces are polished. During polishing, air is drawn through the external air intake into the barrel container by the operation of a dust collector. The drawn air is caused to flow through the polishing chips and workpieces in the barrel container to thereby cool them. Furthermore, dust resulting from polishing is exhausted through the dust exhaust portion to the dust collector side. Thus, loading of the polishing chips due to dust resulting from polishing, which is a problem peculiar to the dry polishing, can be prevented.
There are two methods of manufacturing the barrel container for dry barrel polishing machines. In one method, the steel body 41 is made in the same manner as described above and thereafter, molten polyurethane or the like is cast into the lining 46 which is attached to an inner wall of the body. Subsequently, a plurality of small holes 50 are formed so as to serve as the external air intake and the dust exhaust portion. The polishing chips and workpieces cannot pass through the holes 50. See FIG. 13A. In the other method, a large vent 51 is formed in the body 41. The lining 46 with another vent 52 slightly larger than the vent 51 is cast. Thereafter, a polyurethane piece 5 having small holes 4 is fitted with the vent 52 by bolts etc. as shown in FIG. 13B. Each hole 4 has such a diameter that the polishing chip and workpiece cannot pass therethrough.
In the former method, however, both body 41 and lining 46 need to be simultaneously drilled. It is difficult to form such a small hole, as the holes 50, through which the polishing chips and workpieces cannot pass. The reason for this is that a small hole is closed upon extraction of a drill since polyurethane is an elastomer. Even if holes should be formed, end faces of the holes 50 would be deteriorated as the result of drilling. As a result, the end faces of the holes 50 would be worn such that peripheral portions of the holes are partially worn. The partial wear of the peripheral portions of the holes necessitates replacement of the overall lining, increasing the manufacturing cost.
In the latter method, a steel plate with vent holes 51 is bent into the steel body 41. Thereafter, when the lining is formed, dummy molds are fitted with the vents 51 and 52, respectively, so that the material for the lining can be prevented from flowing into the vents 51 and so that the vents 52 are formed in the lining 46 after completion of the lining. The dummy molds are removed after the material for the lining has been solidified. The polyurethane piece 5 having small holes 4 through which the polishing chips and workpieces cannot pass is attached to the vents 52 by bolts. However, since the steel body 41 has a definite limitation of accuracy with regard to the bending, spring back sometimes results in distortion as shown in FIG. 14 after bending. As a result, a space between the body 41 and the core 44 becomes non-uniform when the lining 46 is formed. One vent 51 is displaced such that a thickness of the lining becomes non-uniform. When the polyurethane piece 5 is fixed to the vent 52 by bolts, a difference results between a thickness of the piece 5 and the thickness of the lining of the vent 52. This difference causes the aforesaid partial wear. A downward force is applied to the body 41 from above particularly when the lid is closed, whereupon the distortion is increased. This increases the difference between the thicknesses of the piece 5 and the lining, resulting in a gap.
Further, polishing chips and workpieces are moved at high speeds in the barrel container in the dry barrel polishing. Accordingly, the polishing chips and workpieces repeatedly collide against the lining wall. When the workpieces are soft, the collision results in marks on the workpieces. Water serves as a buffer in the conventional wet polishing, thereby preventing forming of the marks on the workpieces. Accordingly, the conventional barrel container for the wet barrel polishing has a high hardness from the view point of wear resistance. However, when the container for the dry barrel polishing has the same hardness as that of the wet barrel polishing, the aforesaid marks are formed on the workpieces.
Therefore, an object of the present invention is to provide a barrel container which has an inner wall with no difference in thickness in spite of the presence of a vent, and in which it is difficult for workpieces to incur marks due to collision against the inner wall.
The present invention provides a barrel container for a dry barrel polishing machine, comprising a container body made of an elastic material and having an access opening through which polishing chips and workpieces are put into the container body. The container body has a wall with a through hole providing communication between an exterior and an interior of the container body, and a lid opening and closing the access opening is provided.
According to the above-described barrel container, the container body is made of the elastic material although the conventional casing body is made of steel. Accordingly, the container body has a uniform thickness in spite of the presence of the vents. There is no difference in the thickness even when a piece having the same thickness and formed with small holes is attached to the container body. Furthermore, since the container body is made of the elastic material such as the polyurethane resin, it is light-weight, and a load for carrying the barrel container can be reduced. Furthermore, when the container body is made of the polyurethane resin with high wear and abrasion resistance, the barrel container can be used for a long period of time. Moreover, since the container body of the barrel container has a larger thickness than the lining of the conventional container body made of steel, the service life of the barrel container can further be improved. Additionally, shock due to the collision of workpieces against the inner wall of the container body can be reduced in the dry barrel polishing as compared with the case of the wet barrel treatment. Thus, the marks due to the collision can be reduced.
In a preferred form, the elastic material is polyurethane. In this case, the polyurethane preferably has a hardness ranging between 60 and 80 in ISO 7619 Shore A durometer hardness. Consequently, shock due to the collision of workpieces against the inner wall of the container body can be reduced in the dry barrel polishing as compared with the case of the wet barrel treatment. Thus, the marks due to the collision can be reduced.
In another preferred form, the container body has a hole formed in the wall thereof. In this case, the barrel container further comprises a piece made of an elastic material and having a number of small holes, with the piece being attached to the hole of the wall of the container body. Additionally, the barrel container further comprises a plate mounted on an outer wall of the container body so as to cover the hole, with the plate having air permeability. In this case, the piece is bolted to the plate at an inner wall of the container body.
In a further preferred form, the barrel container further comprises a barrel casing enclosing the container body with a space being defined in the barrel casing so as to communicate via the through hole of the container body with an interior of the container body, and a hollow shaft supporting the barrel container so that the barrel container is rotatable. The shaft has a communication passage defined therein so as to provide communication between the space in the barrel casing and a dust collector.
In still another preferred form, the container body has a hexagonal section and includes two peripheral sides adjacent to the access opening, and a bottom. The peripheral sides and bottom are formed with a plurality of the through holes respectively. The bottom communicates with the space in the barrel casing for exhaust of air, and the two peripheral sides communicate via the barrel casing with an exterior of the barrel casing for intake of air.